Brake adjuster

ABSTRACT

An automatically operative brake adjuster and retract device particularly adapted for a multiple disc brake of the disc type. A fixed outer bushing threadedly engaged with a carrier member slidably contains an inner bushing loaded by a return compression spring interposed between the inner and outer bushings. A radially deformable cylinder fixed to the inner bushing slidably contains a fluid pressure actuated tapered piston having an interference or force fit therein and adapted to deform the cylinder radially outwardly under the influence of applied pressurized fluid on the piston to permit axial movement of the piston therein to the degree necessary for brake application. Brake release in response to depressurization of the piston permits the inner bushing to retract relative to the outer bushing under the influence of the compression spring thereby establishing a predetermined retract position of the cylinder and thus the piston frictionally engaged therewith.

llnite States Eorkowsld 1 BRAKE ADJUSTER [75] Inventor: Donald F.Borkowski, South Bend,

Ind.

[73] Assignee: The Bendix Corporation, -South Bend, Ind.

22 Filed: Mar. 24, 1972 21] App1.No.: 237,778

UNITED STATES PATENTS 2,888,109 5/1959 Tankersley ..188/196 P 3,376,9594/1968 Holcomb et a1. .1 188/196 R 3,542,165

11/1970 Lucien ..l88/196 P FOREIGN PATENTS OR APPLICATIONS 811,5054/1959 Great Britain ..l88/196 R [n] 3,729,72 1 1 Apr. 24,1973

Primary ExaminerDuane A. Reger Attorney-Gordon H. Chenez et al.

1 5 7 ABSTRACT An automatically operative brake adjuster and retractdevice particularly adapted for a multiple disc brake of the disc type.A fixed outer bushing threadedly engaged with a carrier member slidablycontains an inner bushing loaded by a return compression springinterposed between the inner and outer bushings. A radially deformablecylinder fixed to the inner bushing slidably contains a fluid pressureactuated tapered piston having an interference or force fit therein andadapted to deform the cylinder radially outwardly under-the influence ofapplied pressurized fluid on the piston to permit axial movement of thepiston therein to the degree necessary for brake application. Brakerelease in response to depressurization of the piston permits the innerbushing to retract relative to the outer bushing under the influence ofthe compression spring thereby establishing a predetermined retractposition of the cylinder and thus the piston frictionally engagedtherewith.

8 Claims, 3 Drawing Figures BRAKE ADJUSTER BACKGROUND OF THE INVENTIONThe use of disc brake adjuster mechanisms particularly in multiple discaircraft brakes to progressively advance the retracted position of thepiston to compensate for brake wear is well known as is apparent fromnumerous patents such as, for example, US. Pat. No. 3,376,959 issuedApr. 9, 1968, in the name of O. L. Holcomb, Jr., et al (commonassignee). Various adjuster devices have been proposed but those ofwhich I am aware have not been entirely satisfactory for one or morereasons which may include undue weight and/or volume, structuralcomplexity and attendent lack of reliability as well as cost,maintenance difficulties and limited part salvageability for rebuildingpurposes.

SUMMARY OF THE INVENTION The present invention pertains to automaticallyoperating brake adjusting apparatus adapted to compensate forprogressive wear of the brake friction material and maintain brakeoperating clearances substantially constant.

It is an object of the present invention to provide a brake adjusterautomatic in operation and characterized by relatively simple, compactand reliable structure.

It is an object of the present invention to provide brake adjustingapparatus including fluid pressure actuated piston means for energizingthe brake wherein a fluid pressure actuated wedge shaped member havingan interference fit with a deformable cylinder is advanced therethroughas brake wear progresses to maintain a substantially constant range ofmovement of the piston means between brake applied and retractedpositions thereof. It is another object of the present invention toprovide brake adjusting apparatus including fluid pressure actuatedspring loaded piston means movable between brake retracted and appliedpositions and provided with a fluid pressure responsive wedge shapedmember having an interference fit in a deformable cylinder which isdeformed thereby to cause a permanent elongation of the piston means tocompensate for brake wear and maintain the range of travel of saidpiston means substantially constant between the brake retracted andapplied positions.

Additional objects and advantages may become apparent with reference tothe following description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration insection of an aircraft wheel and brake embodying the present invention.

FIG. 2 is a section schematic shown in enlarged form of the presentinvention removed from the conventional wheel and brake structure ofFIG. 1.

FIG. 3 is a sectional view taken on line 3-3 of FIG. 2.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawingsand in particular FIG. I, numeral designates a conventional aircraftwheel and brake assembly including annular wheel half portions 12 and14, only one of which is shown in cross section. The wheel portions 112and B4 are each provided with a tire retaining flange portion 16 forretaining a tire, not shown, thereon. A plurality of circumferentiallyspaced-apart bolt and nut combinations l8 serve to fixedly secure thewheel portions 12 and 14 together. The wheel portion 12 is provided withintegral web portions 20 and a hub portion 22 and is rotatably carriedon a fixed axle 24 by conventional bearing means 26 interposed betweenhub portion 22 and axle 24.

A rotatably fixed annular brake carrier 28 secured to fixed axle 24 bysuitable conventional keys or splines 30 is provided with a plurality ofcircumferentially spaced-apart chambers or cavities 32 only one of whichis shown. An annular torque tube 34 is fixedly secured to brake carrier28 by a plurality of circumferentially spaced-apart bolts 36, only oneof which is shown, extending through mating openings in carrier 28 andthreadedly engaged with torque tube 34. The torque tube 34 is providedwith an integral annular brake backing plate 38 having an annularsection of friction material or lining 40 fixedly secured thereto.

' A plurality of annular brake stator members 42 are interleaved with aplurality of annular brake rotor members 44. The brake stator members 42are each provided with lining 46 fixedly secured to opposite sidesthereof and are suitably keyed as at 48 for axial movement to torquetube 34. The rotor members 44 are suitably keyed for axial movement to aspline member 50 which, in turn, is fixedly secured to wheel portion 12.The interleaved or stacked rotors 44 and stators 42 are adapted to becompressed together between backing plate 38 and a movable pressureplate 52 to provide the desired braking or retardation of the wheel. Thepressure plate 52 has lining 54 fixedly secured thereto and is suitablykeyed as at 56 for axial movement to torque tube 34.

The force imposed on pressure plate 52 tending to compress the statormembers 42 and rotor members 44 is derived from a plurality of fluidmotors or piston assemblies 58 embodying the present invention securedin chambers 32 and responsive to pressurized fluid conducted to chamber32 via a passage 60 from a conventional operator-controlled fluidpressure source, not shown. The fluid motor assemblies 58 each includean outer bushing 62 having a threaded section 64 engageable with matingthreads in carrier 28, a head end 66 having a hexagonal shape orotherwise suitably shaped to receive a wrench and an opposite endportion 68 defining a stop 70 and an annular shoulder 72. The bushing 62is suitably recessed internally and externally to receive fluid sealssuch as O rings 74 and 76.

An inner bushing or sleeve 78 having a radially outwardly extendingannular end portion 80 slidably engaged with the carrier 28 and aradially inwardly extending annular end portion 82. A compression spring84 interposed between shoulder 72 and annular end portion 80 urges innerbushing 78 away from stop 70 into engagement with a suitable fixed stop85 as, for example, the end wall of chamber 32.

A cylinder 86 formed of metal or other suitable deformable material isreceived by inner bushing 78 with one end of cylinder 86 bearing againstannular end portion 82 to prevent axial movement of cylinder 86 as willbe described. The inner wall of bushing 78 is suitably recessed toreceive an ring 88 to thereby provide a fluid seal between adjacentsurfaces of bushing 78 and cylinder 86.

A piston 90 slidably received by cylinder 86 has an interference fittherewith and is provided with a tapered portion 92 which bears againstcylinder 86. The piston 90 is frictionally secured in cylinder 86 byvirtue of the interference fit therebetween which interference fit isovercome by a predetermined force derived from pressurized fluid actingagainst piston 90 as will be described. The piston 90 is suitablyrecessed to receive an O ring 94 thereby establishing a fluid sealbetween adjacent surfaces of cylinder 86 and piston 90.

An extension member 96 having a reduced diameter end 98 which extendsinto a mating recess 100 in piston 90 is fixedly secured to piston 90which is provided with a central stepped opening 102 through which abolt 104 extends into threaded engagement with end 98. The opposite endof extension member 96 is recessed as at 106 to receive a sleeve 108which provides a backing surface for an annular section of suitable heatinsulation material 110 extending through the opening defined by endportion 82. The insulation material 110 as well as sleeve 108 is fixedlysecured in position on member 96 by a retaining cap 112 having a conicalseat for the head of a bolt 114 extending therethrough into threadedengagement with extension member 96. The insulating material 110provides heat insulation between extension member 96 and cap 112 whichbears against pressure plate 52. The end 98 may be chamfered to providea suitable recess containing on O ring 116 or the like which iscompressed to provide a fluid seal between surfaces of end 98 and recess108.

The piston assembly including piston 90, extension member 96, sleeve108, insulation material 110, and cap 112, is pre-assembled and bolts104 and 114 tightened to fixedly secure the parts together. The pistonassembly with O ring 94 therein, is positioned in cylinder 86 and piston90 forced into cylinder 86 to a predetermined axial position as shown inFIG. 1. The O ring 88 is inserted in inner bushing 78 which slidablyreceives cylinder 86 the end of which abuts end portion 82.

The assembled inner bushing 78 and cylinder 86 with the piston assemblytherein is inserted in chamber 32 and compression spring 84 slipped intoposition thereon. The outer bushing 62 with 0" rings 74 and 76positioned thereon is inserted into chamber 32 with spring 84 bearingthereagainst and turned with a suitable wrench to fixedly secure outerbushing 62 in position in carrier 28.

The above described assembly procedure may be reversed for disassemblypurposes. In this manner assembly or disassembly of the fluid motors 58relative to carrier 28 may be carried out quickly with relatively fewtools.

Assuming the wheel and brake assembly to be operatively mounted on theaircraft, the piston or fluid motor assemblies 58 are energized bypressurized fluid introduced to chambers 32 via passages 60. Thepressurized fluid acts against the exposed ends of inner bushing 78,cylinder 86 and piston 90 thereby overcoming the force of spring 84 andurging the end portion into engagement with stop 70. The pressure plate52 under the influence of piston carried by inner bushing 78 is urgedagainst the stack of rotors and stators 44 and 42 tending to compressthe same against backing plate 38 thereby establishing the desiredfrictional engagement to retard wheel portions 12 and 14.

Wear of the friction lining 40, 46 and/or 54 results in an increase inthe axial spacing between the frictionally engageable surfaces which, inturn, must be compensated for if the rotors and stators 44 and 42 are tobe fully engaged during brake energization. Assuming that such wearexists, it will be recognized that engagement of end portion 80 withstop 70 will have the effect of limiting travel of piston 90 and thuspressure plate 52 short of that required to cause full engagement ofrotors and stators 44 and 42. However, the force derived from thepressurized fluid acting against piston 90 is, in part, imposed radiallyoutwardly against cylinder 86 by virtue of the tapered portion 92bearing thereagainst. The cylinder 86 is deformed radially outwardlythereby permitting piston 90 to advance axially through cylinder 86 andthus pressure plate 52 toward backing plate 38 to the position necessaryto compensate for the wear of the friction lining thereby establishingfull engagement of rotors and stators 44 and 42. It will be noted thatsufficient clearance is provided between inner bushing 78 and cylinder86 to permit outward deformation of cylinder 86 as piston 90 advancestherethrough. The angle of taper of tapered portion 92 is selected toprovide adequate frictional engagement to hold piston 90 in positionrelative to cylinder 86 at any given position of the piston therein whenthe pressurized fluid is reduced to release the brake.

The piston 90 and thus pressure plate 52 is retracted a predeterminedaxial distance upon release of the brake. To that end, a drop inpressure in chamber 38 allows inner bushing 78 carrying cylinder 86 andpiston 90 to retract under the influence of spring 84 and abut the endwall of chamber 38 thereby limiting the retraction accordingly toestablish a predetermined running clearance between the frictionallyengageable surfaces of the brake.

The fluid motor or piston assemblies 58 may be rebuilt for reuse with aminimum of parts replacement thereby reducing cost accordingly. It willbe noted that upon disassembly of the piston assembly 58 from thecarrier 38 the cylinder 86 with piston 90 and attachments thereto may beremoved from inner bushing 78. The piston 90 and attachments thereto areremoved from cylinder 86 and inserted in a new cylinder 86 in heheretofore mentioned manner of assembly.

It is readily apparent that applicant's heretofore described brakeadjuster apparatus provides a simple, relatively compact and lightweightbrake adjuster mechanism capable of compensating for lining wear andretracting the brake to maintain a constant running clearance when thebrake is released.

lclaim:

1. Brake adjusting apparatus for a brake assembly having a predeterminedrunning clearance and energized by pressurized fluid, said brakeadjusting apparatus comprising:

a chamber having a fluid connection with a controlled source ofpressurized fluid;

a bushing removably secured in said chamber;

a sleeve member slidably carried by said bushing for axial movementtherein;

a first fixed stop engageable with said sleeve member for limitingmovement thereof in a brake-applying direction;

a second fixed stop engageable with said sleeve member for limitingmovement thereof in a brake release direction;

resilient means urging said sleeve member into engagement with saidsecond stop;

a radially deformable cylinder carried by said sleeve member and movabletherewith; and

piston means slidably carried by said cylinder and having aninterference fit therewith;

said piston means being responsive to said pressurized fluid andtogether with said sleeve member movable in a brake-applying direction;

said sleeve member being engageable with said first stop whereupon saidpiston means is forcibly urged through said cylinder causing radialoutward deformation thereof to reposition said piston means axiallytherein to the extent provided by unwanted brake clearancebetweenfrictionally engageable members of the brake;

said pressurized fluid being released to permit retraction of saidsleeve member into engagement with said second stop in response to saidresilient means to establish a predetermined brake running clearance.

2. Brake adjusting apparatus for a brake assembly as claimed in claim 1,wherein:

said chamber is defined by a carrier member; and

said bushing is threadedly engaged with said carrier member.

3. Brake adjusting apparatus for a brake-assembly as claimed in claim 2,wherein:

said first stop is defined by an axially extending annular portion ofsaid bushing; and

said sleeve is provided with a radially outwardly extending flangeengageable with said first stop.

4. Brake adjusting apparatus for a brake assembly as claimed in claim 3wherein:

said resilient means is a compression spring interposed between saidbushing and said flange. 5. Brake adjusting apparatus for a brakeassembly as claimed in claim 1, wherein:

said piston means is provided with a radially inwardly tapering portionengageable with said cylinder and operative to deform said cylinderradially outwardly.

6. Brake adjusting apparatus for a brake assembly as claimed in claim 1,wherein:

claimed in claim 6, wherein:

said cylinder is concentric with said sleeve and engageable at one endwith said radially inwardly extending end ortion of said sleeve. 8.Brake ad us mg apparatus for a brake assembly as claimed in claim 1,wherein: j

said piston means is frictionally secured in said cylinder in theabsence of said pressurized fluid tending to apply the brake.

1. Brake adjusting apparatus for a brake assembly having a predeterminedrunning clearance and energized by pressurized fluid, said brakeadjusting apparatus comprising: a chamber having a fluid connection witha controlled source of pressurized fluid; a bushing removably secured insaid chamber; a sleeve member slidably carried by said bushing for axialmovement therein; a first fixed stop engageable with said sleeve memberfor limiting movement thereof in a brake-applying direction; a secondfixed stop engageable with said sleeve member for limiting movementthereof in a brake release direction; resilient means urging said sleevemember into engagement with said second stop; a radially deformablecylinder carried by said sleeve member and movable therewith; and pistonmeans slidably carried by said cylinder and having an interference fittherewith; said piston means being responsive to said pressurized fluidand together with said sleeve member movable in a brake-applyingdirection; said sleeve member being engageable with said first stopwhereupon said piston means is forcibly urged through said cylindercausing radial outward deformation thereof to reposition said pistonmeans axially therein to the extent provided by unwanted brake clearancebetween frictionally engageable members of the brake; said pressurizedfluid being released to permit retraction of said sleeve member intoengagement with said second stop in response to said resilient means toestablish a predetermined brake running clearance.
 2. Brake adjustingapparatus for a brake assembly as claimed in claim 1, wherein: saidchamber is defined by a carrier member; and said bushing is threadedlyengaged with said carrier member.
 3. Brake adjusting apparatus for abrake-assembly as claimed in claim 2, wherein: said first stop isdefined by an axially extending annular portion of said bushing; andsaid sleeve is provided with a radially outwardly extending flangeengageable with said first stop.
 4. Brake adjusting apparatus for abrake assembly as claimed in claim 3 wherein: said resilient means is acompression spring interposed between said bushing and said flange. 5.Brake adjusting apparatus for a brake assembly as claimed in claim 1,wherein: said piston means is provided with a radially inwardly taperingportion engageable with said cylinder and operative to deform saidcylinder radially outwardly.
 6. Brake adjusting apparatus for a brakeassembly as claimed in claim 1, wherein: said sleeve member is providedwith a radially inwardly extending end portion defining an opening; saidpiston means is provided with a reduced diameter portion including asection of heat insulation material fixedly secured thereto andextending through said opening into engagement with the heat generatingfrictionally engageable portion of the brake.
 7. Brake adjustingapparatus for a brake assembly as claimed in claim 6, wherein: saidcylinder is concentric with said sleeve and engageable at one end withsaid radially inwardly extending end portion of said sleeve.
 8. Brakeadjusting apparatus for a brake assembly as claimed in claim 1, wherein:said piston means is frictionally secured in said cylinder in theabsence of said pressurized fluid tending to apply the brake.